Swivel joint for oilfield pumping stimulation

ABSTRACT

A swivel joint comprises a tubular female member which is rotatably connected to a tubular male member. The female member includes a female race portion having an axially extending inner annular recess, a female inner end portion which is formed at an axially inner end of the recess, and a number of inner annular grooves which are formed in the recess coaxially therewith. The male member includes a male race portion having an annular outer surface which is configured to be received in the recess, a male nose portion which is formed at an end of the male race portion, and a number of outer annular grooves which are formed on the outer surface coaxially therewith. The male race portion is positioned in the female race portion such that the male nose portion is located adjacent the female inner end portion and each outer groove is aligned with a corresponding inner groove to thereby define a number of annular bearing races within which a plurality of balls are received to thereby rotatably connect the male member to the female member. The swivel joint includes a first primary seal which is positioned between the male nose portion and the female inner end portion, and a second primary seal which is positioned between the male nose portion and the female inner end portion radially outwardly of the first primary seal. The male and female members define a flow bore through the swivel joint which is sealed by the first primary seal and, in the event of a failure of the first primary seal, the second primary seal.

The present invention is directed to swivel joint. More particularly,the invention is directed to a swivel joint which includes both firstand second primary seals between the male and female portions of theswivel joint to increase the useful life of the swivel joint.

BACKGROUND OF THE INVENTION

Swivel joints are commonly used in the oilfield industry to build rigidyet dynamically configurable flow lines between various pieces ofequipment. For example, in oilfield pumping stimulation operations, orfracking operations, swivel joints are often used to connect a number ofhigh pressure pumping units to a manifold and to connect the manifold toan injection wellhead.

These types of swivel joints typically comprise a tubular male memberwhich is rotatably connected to a tubular female member. The male membercomprises a male race and the female member comprises a female racewhich is configured to be receive the male race. When the male race ispositioned in the female race, each of a plurality of outer annulargrooves on the male race is aligned with a corresponding inner annulargroove on the female race to thereby form plurality of bearing raceswithin which a plurality of balls are received to rotatably connect themale member to the female member.

When the male and female members are connected together, an annul isformed between the male and female races which is in fluid communicationwith the flow bore defined by the swivel joint. In order to contain thefracking fluid within the flow bore while still allowing the male andfemale members to rotate relative to each other, the swivel jointusually includes a dynamic primary seal which is positioned between anose portion of the male race and an inner end portion of the femalerace.

However, if the primary seal fails, the flow of pressurized frackingfluid through the annulus can quickly erode the male nose portion and/orthe female inner end portion and thereby cause the swivel joint to fail.Also, pressurized fluid will enter the annulus and generate hydrostaticend loads between the male and female races which could cause thebearing races to fail.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other limitations inthe prior art are addressed by providing a swivel joint which includes atubular female member that is rotatably connected to a tubular malemember. The female member includes a female race portion having anaxially extending inner annular recess, a female inner end portion whichis formed at an axially inner end of the recess, and a number of innerannular grooves which are formed in the recess coaxially therewith. Themale member includes a male race portion having an annular outer surfacewhich is configured to be received in the recess, a male nose portionwhich is formed at an end of the male race portion, and a number ofouter annular grooves which are formed on the outer surface coaxiallytherewith. The male race portion is positioned in the female raceportion such that the male nose portion is located adjacent the femaleinner end portion and each outer groove is aligned with a correspondinginner groove to thereby define a number of annular bearing races withinwhich a plurality of balls are received to thereby rotatably connect themale member to the female member. The swivel joint further includes afirst primary seal which is positioned between the male nose portion andthe female inner end portion, and a second primary seal which ispositioned between the male nose portion and the female inner endportion radially outwardly of the first primary seal. Thus, the male andfemale members define a flow bore through the swivel joint which issealed by the first primary seal and, in the event of a failure of thefirst primary seal, the second primary seal.

In accordance with one embodiment of the invention, the second primaryseal is mounted in an annular seal pocket which is formed in the femaleinner end portion. The second primary seal may comprise in cross sectiona generally rectangular base portion which is positioned at leastpartially in the seal pocket and an annular ridge portion which extendsradially inwardly from the base portion and sealingly engages the malenose portion. The annular ridge portion may comprise in cross section aradially inner peak and a beveled portion which diverges radiallyoutwardly from the peak in a direction toward an axially outer end ofthe recess. In this embodiment, the beveled portion sealingly engages aconical sealing surface which is formed on the male nose portionopposite the seal pocket, and the peak sealingly engages a cylindricalsealing surface which is formed on the male nose portion axiallyinwardly of the conical sealing surface. Also, the second primary sealmay comprise an annular non-extrusion spring which is located proximatean intersection of the base portion and the beveled portion.

In accordance with another embodiment of the invention, the male noseportion comprises an end wall which extends radially outwardly from theflow bore and a cylindrical side wall which extends axially outwardlyfrom the end wall, and the first primary seal sealing engages the endwall and the second primary seal sealingly engages the cylindrical sidewall. The male nose portion may also comprise a conical side wall whichdiverges radially outwardly from the cylindrical side wall in adirection toward the axially outer end of the recess. In this case, thesecond primary seal sealingly engages both the cylindrical side wall andthe conical side wall. In this embodiment, the second primary seal maycomprise in cross section a radially inner peak and a beveled portionwhich diverges radially outwardly from the peak in a direction toward anaxially outer end of the recess, in which event the annular peaksealingly engages the cylindrical side wall and the beveled portionsealingly engages the conical side wall.

In accordance with a further embodiment of the invention, the secondprimary seal comprises a generally rectangular cross section having afirst axially outer sealing face which sealingly engages a radiallyextending first end wall on the male nose portion. In this embodiment,the first primary seal may be mounted in an annular seal pocket which isformed in the female inner end portion, in which event the first primaryseal comprises a generally rectangular cross section having a secondaxially outer sealing face which sealingly engages a radially extendingsecond end wall that is formed on the male nose portion radially andaxially inwardly of the first end wall. Moreover, the second end wallmay extend radially outwardly from the flow bore and be connected to thefirst end wall by an axially extending cylindrical side wall.

In accordance with still another embodiment of the invention, the swiveljoint includes an annulus which is formed between the female inner endportion and the male nose portion and is connected to the flow bore. Theannulus comprises a portion which extends between the second primaryseal and an axially innermost bearing race, and the swivel joint furtherincludes a leak detection port which extends through the female memberto the annulus portion. In this manner, a failure of both the first andsecond primary seals can be detected by observing whether fluid from theflow bore is escaping through the leak detection port.

In accordance with another embodiment of the invention, the swivel jointincludes a monitor port which extends through the female member to aportion of the annulus that extends between the first and second primaryseals. The monitor port is sealed by a removable plug, and a failure ofthe first primary seal can be detected by removing the plug anddetermining whether fluid from the flow bore has entered the monitorport.

In accordance with still another embodiment of the invention, the swiveljoint includes a monitor port which extends through the female member toa portion of the annulus that extends between the first and secondprimary seals, a plug member which is positioned in the monitor port,and a plug holder which is positioned in the monitor port radiallyoutwardly of the plug member and comprises an axial through bore. Theplug is configured such that, in the event of a failure of the firstprimary seal, pressure in the annulus portion will force at least aportion of the plug through the axial through bore to thereby provide avisual indication that the first primary seal has faded. The swiveljoint may further comprise a retainer which is secured in the monitorport radially outwardly of the plug holder to thereby secure the plugholder in the monitor port, and a keeper which is positioned in themonitor port between the plug holder and the retainer. In thisembodiment, the keeper comprises a cavity on its radially inner endwhich is aligned with the through bore and into which the portion of theplug will extrude in the event of a failure of the first primary seal.Also, an annular portion of the plug holder surrounding the through boremay be sealed to the monitor port and a radially inner end of the keepermay be sealed to a radially outer end of the plug holder over thethrough bore to thereby retain the pressure in the monitor port.

Thus, the second primary seal provides an effective means for extendingthe useful life of the swivel joint. Should the first primary seal fail,the second primary seal will prevent high pressure fracking fluid fromflowing through the annulus at a rate which would otherwise cause themale nose portion and/or the female inner end portion to wash out. As aresult, if the first primary seal fails, the useful life of the swiveljoint can be extended by simply replacing the first primary seal. Also,with the second primary seal in place, a failure of the first primaryseal does not result in a total rupture of the seal. Rather, the firstprimary seal will act as a labyrinth seal and restrict the flow of solidfracking materials to the second primary seal. Therefore, a failure ofthe first primary seal will not result in erosion of the sealingsurfaces.

Furthermore, since the cylindrical sealing surface is radially proximatethe end wall against which the first primary seal is sealingly engaged,a failure of the first primary seal will result in manageable increasesin the hydrostatic end loads on the male and female race portions.Moreover, since the conical sealing surface extends radially outwardlyfrom the cylindrical sealing surface, the radial cross section of themale nose portion remains substantial, thus making the swivel jointsuitable for erosive applications. Additionally, since the annular peakof the second primary seal is located both radially and axially inwardlyof the beveled portion of the seal, pressure in the annulus will forcethe annular ridge portion into tighter sealing engagement with theconical sealing surface in a manner similar to a pressure energizedseal. Therefore, the second primary seal will provide an effective sealwhich will allow the swivel joint to remain in service until the firstprimary seal can be replaced.

These and other objects and advantages of the present invention will nowbe described with reference to the accompanying drawings. In thedrawings, the same reference numbers may be used to denote similarcomponents in the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a first embodiment of the swiveljoint of the present invention;

FIG. 2 is an enlarged cross sectional view of the male and female raceportions of the swivel joint of FIG. 1;

FIG. 3 is an enlarged cross sectional view of a portion of the male andfemale race portions shown in FIG. 2;

FIG. 4 is an enlarged cross sectional view of the primary swivel jointseal shown in FIG. 3;

FIG. 5 is an enlarged cross sectional view of the male and female raceportions of a second embodiment of the swivel joint of the presentinvention;

FIG. 6 is an enlarged cross sectional view of the first and secondprimary seals used in the swivel joint of FIG. 5;

FIG. 7 is an enlarged cross sectional view of the male and female raceportions of a third embodiment of the swivel joint of the presentinvention; and

FIG. 8 is an enlarged cross sectional view of the male and female raceportions of a fourth embodiment of the swivel joint of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the swivel joint of the present invention is shownin FIG. 1. The swivel joint of this embodiment, generally 10, includes atubular male member 12 which is rotatably connected to a tubular femalemember 14 to thereby form a fluid pipe component that can be connectedto other pipe components (not shown) in a known manner to build aconfigurable flow line which can be used to connect, e.g., a pumpingunit to an injection wellhead for use in well tracking operations.Although the male and female members 12, 14 are depicted as beingL-shaped, they can have any conventional configuration. For example, oneor both of the male and female members 12, 14 may be straight.

The male member 12 includes a first end 16 which is connectable toanother pipe component and a second end which is configured as a malerace portion 18. Similarly, the female member 14 includes a first end 20which is connectable to another pipe component and a second end which isconfigured as a female race portion 22. The male and female raceportions 18, 22 comprise a common axial centerline CL and are connectedtogether (as ill be described below) such that the male and femalemembers 12, 14 are rotatable relative to each other about the centerlineCL.

Referring also to FIG. 2, the male race portion 18 comprises an annularouter surface 24, a number (in this case three) of outer annular grooves26 which are formed on the outer surface coaxially with the centerlineCL, and a male nose portion 28 which is formed at the end of the malemember 12. The female race portion 22 includes an axially extendinginner annular recess 30 which is configured to receive the outer surface24 of the male race portion 18, a number (in this case three) of innerannular grooves 32 which are formed in the recess coaxially with thecenterline CL, and a female inner end portion 34 which is formed at anaxially inner end of the recess. As used herein, the terms “axiallyinner” and “axially outer” are referenced to the recess 30. Thus, theterm “axially inner” refers to innermost end of the recess 30, which isthe left end of the recess as viewed in FIG. 2, and the term “axiallyouter” refers to the end of the recess which coincides with the end ofthe female member 14.

As shown in FIG. 2, when the male race portion 18 is positioned in therecess 30, the male nose portion 28 is located adjacent the female innerend portion 34. In this position, each of the outer annular grooves 26is aligned with a corresponding inner annular groove 32 to thereby forman equal number of bearing races within which a plurality of balls 36are received to thereby rotatably connect the male member 12 to thefemale member 14. When so connected, the male and female members 12, 14define a continuous flow bore 38 through the swivel joint 10.

When the male and female members 12, 14 are connected as just described,an annulus 40 is formed between the male and female race portions 18,22. In order to contain the pressure within the flow bore 38 while stillallowing the male and female members 12, 14 to rotate relative to eachother, the swivel joint 10 is provided with a dynamic first primary seal42 which is positioned between the male nose portion 28 and the femaleinner end portion 34. Referring also to FIG. 3, the first primary seal42 is mounted in a first seal pocket 44 which is formed in the femaleinner end portion 34. The first seal pocket 44 may comprise, forexample, a first end wall 46 which extends radially outwardly from theflow bore 38 and a cylindrical first sidewall 48 which extends axiallyoutwardly from the first end wall. In this example, the first primaryseal 42 comprises a generally rectangular cross section having anaxially outer sealing face 50 that engages a radially extending secondend wall 52 on the male nose portion 28. The first primary seal 42 mayalso include a non-extrusion ring 53 which is positioned adjacent theannulus 40.

Should the primary seal 42 fail, the flow of pressurized fracking fluidthrough the annulus 40 can quickly erode the male nose portion 28 and/orthe female inner end portion 34 and thereby cause the swivel joint 10 tofail. In accordance with the present invention, this problem isaddressed by providing the swivel joint 10 with a dynamic second primaryseal 54 between the male nose portion 28 and the female inner endportion 34 radially outwardly of the first primary seal 42. In thisregard, a “primary seal” is one which is capable of sealing against theline pressure for which the swivel joint is rated. For example, if theswivel joint is designed to handle a pressure of 15,000 psi, the primaryseal must be capable of sealing against this pressure.

In the event of a failure of the primary seal 42, pressurized fluid willenter the annulus 40 and generate hydrostatic end loads between the malenose portion 28 and the female inner end portion 34 which could causethe male and/or female race portions 18, 22 to fail. In order tominimize these hydrostatic end loads, the second primary seal 54 shouldbe positioned as close to the flow bore 38 as possible. However, if thesecond primary seal 54 is positioned too close to the flow bore, theradial cross section of the male nose portion 28 may be too thin forhighly erosive applications.

In accordance with the present invention, therefore, the swivel joint 10is configured such that the second primary seal 54 seals against themale nose portion 28 only slightly radially outwardly of the end wall 52against which the first primary seal 42 seals. In addition, the secondprimary seal 54 is mounted in a seal pocket which is ideally located inthe female inner end portion 34 rather than the male nose portion 28. Inthis manner, should the first primary seal 42 fail, the second primaryseal 54 will contain the pressure relatively close to the flow bore 38,which will accordingly minimize the hydrostatic end loads between themale nose portion 28 and the female inner end portion 34 that couldotherwise cause the male and/or female race portions 18, 22 to fail.Also, since the seal pocket for the second primary seal 54 is located inthe female inner end portion 34, the seal pocket does not reduce theradial cross section of the male nose portion 28 and the swivel joint 10will consequently be better able to withstand highly erosive fluids.

As shown in FIG. 3, the second primary seal 54 is mounted in a secondseal pocket 56 which is formed in the female inner end portion 34 bothradially and axially outwardly of the first primary seal 42. The secondseal pocket 56 comprises a generally rectangular cross section whichincludes an axially extending floor 58 and two radially extending,axially inner and outer side walls 60, 62.

Referring also to FIG. 4, the second primary seal 54 comprises in crosssection a generally rectangular base portion 64 which is positioned atleast partially in the second seal pocket 56 and an annular ridgeportion 66 which extends radially inwardly from the base portion andsealingly engages the male nose portion 28. Specifically, the annularridge portion 66 may comprise in cross section a radially inner peak 68and a beveled portion 70 which diverges radially outwardly from thepeak. In this embodiment, the beveled portion 70 sealingly engages aconical side wall or sealing surface 72 which is formed on the male noseportion 28 opposite the second seal pocket 56 and the annular peak 68sealingly engages a cylindrical side wall or sealing surface 74 which isformed on the male nose portion axially inwardly of the conical sealingsurface. An advantage of mounting the second primary seal 54 in thefemale inner end portion 34 and locating the sealing surfaces 72, 74 onthe male nose portion 28 is that these sealing surface are readilyaccessible prior to assembly of the swivel joint 10 and can therefore beeasily machined, polished and inspected.

Thus, the second primary seal 54 provides a particularly effective meansfor extending the useful life of the swivel joint 10. Should the firstprimary seal 42 fail, the second primary seal 54 will prevent the highpressure tracking fluid from flowing through the annulus 40 at a ratewhich would otherwise cause the male nose portion 28 and/or the femaleinner end portion 34, and in particular the second end wall 52 againstwhich the first primary seal 42 normally seals, to rapidly erode or“wash out”. As a result, if the first primary seal 42 fails, the usefullife of the swivel joint 10 can be extended by simply replacing thefirst primary seal. Also, the inventors have discovered that, with thesecond primary seal 54 in place, a failure of the first primary seal 42does not result in a total rupture of the seal. Rather, the firstprimary seal 42 will act as a labyrinth seal that will restrict the flowof solid fracking materials to the second primary seal 54. Therefore, afailure of the first primary seal 42 will not result in erosion of thesealing surfaces 72, 74.

Furthermore, since the cylindrical sealing surface 74 is radiallyproximate the end wall 52 against which the first primary seal 42 isengaged, a failure of the first primary seal will result in manageableincreases in the hydrostatic end loads on the male and female raceportions 18, 22. Moreover, since the conical sealing surface 72 extendsradially outwardly from the cylindrical sealing surface 74, the radialcross section of the male nose portion 28 remains substantial, thusmaking the swivel joint 10 suitable for erosive applications.Additionally, since the annular peak 68 of the second primary seal 54 islocated both radially and axially inwardly of the beveled portion 70 ofthe seal, pressure in the annulus 40 will force the annular ridgeportion 66 into tighter sealing engagement with the conical sealingsurface 72 in a manner similar to a pressure energized seal. Therefore,the second primary seal 54 will provide an effective seal which willallow the swivel joint 10 to remain in service until the first primaryseal 42 can be replaced.

Although not required, the second primary seal 54 may also comprise anannular non-extrusion spring 76 which is molded into the seal proximatean intersection of the base portion 64 and the beveled portion 70, whichas shown in FIG. 3 is adjacent the annulus 40 between the male noseportion 28 and the female inner end portion 34. Accordingly, thenon-extrusion spring 76 will minimize the likelihood that the secondprimary seal 54 will extrude into the annulus 40 should the firstprimary seal 42 fail.

Referring still to FIG. 3, the swivel joint may comprise an optionalleak detection port 78 which extends through the female race portion 22to a portion of the annulus 40 located between the second primary seal54 and the axially innermost bearing race defined by the inner and outerannular grooves 26, 32. This portion of the annulus 40 is preferablyisolated from the axially innermost bearing race by a leak detectionseal 80, such as an O-ring, which is positioned in an annular sealgroove 82 in the female inner end portion 34. As shown in FIG. 3, theseal groove 82 may comprise a circular cross section which conforms tothe cross section of the seal 80 in order to securely retain the seal inposition against pressure in the annulus 40 should both the first andsecond primary seals 42, 54 fail. In the event of a failure of both ofthese seals, tracking fluid in the flow bore 38 will flow through theannulus 40 and the leak detection port 78 and out to the atmosphere.Consequently, pressure will not be allowed to build up in the annulus 40and the seal 80 will prevent sand and fracking fluid from entering thebearing races.

Another embodiment of the swivel joint of the present invention is shownin FIG. 5. The swivel joint of this embodiment, generally 100, issimilar in many respects to the swivel joint 10 described above.Therefore, only the male and female race portions 18, 22 are depicted inFIG. 5, and only those portions of the swivel joint 100 which differfrom the swivel joint 10 will be described. As with the swivel joint 10,the swivel joint 100 includes a dynamic first primary seal 102 which ismounted between the male nose portion 28 and the female inner endportion 34 and a dynamic second primary seal 104 which is mountedbetween the male nose portion and the female inner end portion radiallyoutwardly of the first primary seal.

Referring also to FIG. 6, the first primary seal 102 is similar to thefirst primary seal 42 discussed above. Accordingly, the first primaryseal 102 is mounted in a first seal pocket 44 which is formed in thefemale inner end portion 34. The first seal pocket 44 includes a firstend wall 46 which extends radially outwardly from the flow bore 38 and acylindrical first sidewall 48 that extends axially outwardly from thefirst end wall. As the first primary seal 42, the first primary seal 102comprises a generally rectangular cross section having an axially outersealing face 50 that sealingly engages a radially extending second endwall 52 on the male nose portion 28 to thereby seal the annulus 40 fromthe flow bore 38. The first primary seal 102 may also include anon-extrusion ring 54 which is positioned adjacent the annulus 40.

In accordance with the present embodiment, the second primary seal 104is similar in configuration to the first primary seal 102 and is mountedin a second seal pocket 106 which is formed in the female inner endportion 34. The second seal pocket 106 includes a third end wall 108which, after an optional step 110 to accommodate the male nose portion28, extends radially outwardly from the cylindrical first sidewall 48,and a cylindrical second sidewall 112 which extends axially outwardlyfrom the third end wall. As with the first primary seal 102, the secondprimary seal 104 comprises a generally rectangular cross section havingan axially outer sealing face 114 that sealingly engages a radiallyextending fourth end wall 116. The fourth end wall 116 is formed on themale nose portion 28 radially and axially outwardly of the second endwall 52, and in this case the fourth end wall is connected to the secondend wall by a third cylindrical side wall 118. The first primary seal102 may also include a non-extrusion ring 120 which is positionedadjacent the annulus 40.

In comparison to the second primary seal 54 of the swivel joint 10, thesecond primary seal 104 seals against the male nose portion 28 at aslightly larger radius. Thus, in the event of a failure of the firstprimary seal 102, the hydrostatic end loads generated between the maleand female race portions 18, 22 will be somewhat greater than thoseexperienced in the swivel joint 10. Nevertheless, the second primaryseal 104 will prevent wash out the male nose portion 28 and/or thefemale inner end portion 34 and substantially increase the useful lifeof the swivel joint 100. Also, since the second seal pocket 106 isformed in the female inner end portion 34, the radial cross section ofthe male nose portion 28 can be designed sufficiently large to make theswivel joint 100 suitable for erosive applications.

In accordance with a further embodiment of the invention, the swiveljoint may include means for monitoring the condition of the firstprimary seal. Some examples of such monitoring means will now bedescribed in the context of the swivel joint 100 discussed above, itbeing understood that the monitoring means can be incorporated into theswivel joint 10 in a similar manner.

On example of a monitoring means for the first primary seal 102 is shownin FIG. 7. In this embodiment, the monitoring means includes a monitorport 122 which extends through the female race portion 22 to a portionof the annulus 40 located between the first and second primary seals102, 104. Curing normal operation of the swivel joint 100, the monitorport 120 is sealed by a removable plug 124. During pressure testing ofthe first primary seal 102, the plug 124 is removed and the flow bore 38is pressurized up to a predetermined pressure. If the first primary seal102 cannot hold this pressure, which is an indication that the firstprimary seal has faded, the swivel joint 100 can be taken out of serviceand the first primary seal replaced. The swivel joint 100 can thus berepaired prior to the second primary seal 104 failing, which asdiscussed above could cause irreversible damage to the male nose portion28 and/or the female inner end portion 34 that would render the swiveljoint unsuitable for further service. When the swivel joint 100 is innormal service, the plug 124 may be removed during periodic inspectionsto determine if (racking fluid has leaked past the first primary seal102 and into the monitor port 122. If so, the swivel joint 100 can beused until a predetermined life cycle of the second primary seal 104 hasexpired, or the swivel joint can taken out of service and the firstprimary seal 102 replaced prior to a failure of the second primary seal.

Another embodiment of a monitoring means for the first primary seal 102is shown in FIG. 8. Similar to the embodiment just described, themonitoring means of the present embodiment includes a monitor port 122which extends through the female race portion 22 to a portion of theannulus 40 located between the first and second primary seals 102, 104.A plug 126 is positioned in the monitor port 122 in communication withthe annulus 40. The plug 126 includes a stem portion 128 which isreceived in an axial recess 130 in the radially inner end of a plugholder 132. The plug holder 132 includes an axial through bore 134 whichis connected to the recess 130 and an annular shoulder 136 on itsradially inner end which ideally forms a metal-to-metal seal with acorresponding annular seat in the monitor port 122. A keeper 138 ispositioned in the monitor port 122 radially outwardly of the plug holder132. The keeper 138 comprises a cavity 140 in its radially inner endwhich is aligned with the through bore 134 in the plug holder 132. Theradially inner end of the keeper 138 preferably forms a metal-to-metalseal with the radially outer end of the plug holder 132 which, togetherwith the metal-to-metal seal between the monitor port 122 and theannular shoulder 136 on the plug holder, is sufficient to contain anypressure that should leak past the first primary seal 102. A retainer142 is secured in the monitor port 122 radially outwardly of the keeper138 to thereby retain the plug 126, the plug holder 132 and the keeperin position in the monitor port. The retainer 142 may be secured to themonitor port 122 with, e.g., slotted threads to prevent pressure frombeing trapped between the retainer and the keeper 138.

In this embodiment of the monitoring means, the plug 126 is formed of arelatively soft but preferably resilient material, such as rubber.Consequently, in the event of a failure of the first primary seal 102,pressure in the annulus 40 will enter the monitor port 122 and force theplug 126 to extrude through the through bore 134 in the plug holder 132and into the cavity 140 of the keeper 138. Thus, one can determinewhether the first primary seal 102 has developed a leak by removing theretainer 142 and the keeper 138 and seeing whether a portion of the plug128 has extruded past the plug holder 132. If so, the swivel joint 100can be removed from service and the first primary seal 102 removed andreplaced before a leak develops in the second primary seal 104.

In combination with the second primary seal 104, therefore, themonitoring means can be used to extend the useful life of the swiveljoint 100. By using the monitoring means to check the sealing integrityof the first primary seal 102 on a regular basis, a failure of the firstprimary seal can be detected prior to a failure of the second primaryseal 104. As in the case of a prior art swivel joint with a singleprimary seal, a failure of both the first and second primary seals 102,104 could result in erosion of the ale nose portion 28 and the femaleinner end portion 34 and/or a failure of the male and female raceportions 18, 22, either of which would require the swivel joint to bereplaced. Thus, the useful life of the swivel joint can be extended bysimply replacing the first primary seal 102 once it has been found tohave failed and before the second primary seal 104 fails.

It should be recognized that, while the present invention has beendescribed in relation to the preferred embodiments thereof, thoseskilled in the art may develop a wide variation of structural andoperational details without departing from the principles of theinvention. For example, the various elements shown in the differentembodiments may be combined in a manner not illustrated above.Therefore, the appended claims are to be construed to cover allequivalents falling within the true scope and spirit of the invention.

What is claimed is:
 1. A swivel joint comprising: a tubular femalemember which includes a female race portion having an axially extendinginner annular recess, a female inner end portion which is formed at anaxially inner end of the recess, and a number of inner annular grooveswhich are formed in the recess coaxially therewith; a tubular malemember which includes a male race portion having an annular outersurface which is configured to be received in the recess, a male noseportion which is formed at an end of the male race portion, and a numberof outer annular grooves which are formed on the outer surface coaxiallytherewith; wherein the male race portion is positioned in the femalerace portion such that the male nose portion is located adjacent thefemale inner end portion and each outer groove is aligned with acorresponding inner groove to thereby define a number of annular bearingraces within which a plurality of balls are received to therebyrotatably connect the male member to the female member; a first primaryseal which is positioned between the male nose portion and the femaleinner end portion; and a second primary seal which is positioned betweenthe male nose portion and the female inner end portion radiallyoutwardly of the first primary seal; wherein the male and female membersdefine a flow bore through the swivel joint which is sealed by the firstprimary seal and, in the event of a failure of the first primary seal,the second primary seal; wherein the male nose portion comprises an endwall which extends radially outwardly from the flow bore and acylindrical side wall which extends axially outwardly from the end wall,and wherein the first primary seal sealing engages the end wall and thesecond primary seal sealingly engages the cylindrical side wall; andwherein the second primary seal is mounted in an annular seal pocketwhich is formed in the female inner end portion, said seal pocketcomprising a floor and first and second radially outwardly extendingside walls between which the second primary seal is positioned.
 2. Theswivel joint of claim 1, wherein the second primary seal comprises incross section a generally rectangular base portion which is positionedat least partially in the seal pocket and an annular ridge portion whichextends radially inwardly from the base portion and sealingly engagesthe male nose portion.
 3. The swivel joint of claim 2, wherein theannular ridge portion comprises in cross section a radially inner peakand a beveled portion which diverges radially outwardly from the peak ina direction toward an axially outer end of the recess.
 4. The swiveljoint of claim 3, wherein the beveled portion sealingly engages aconical sealing surface which is formed on the male nose portionopposite the seal pocket.
 5. The swivel joint of claim 4, wherein thepeak sealingly engages a cylindrical sealing surface which is formed onthe male nose portion axially inwardly of the conical sealing surface.6. The swivel joint of claim 3, wherein the second primary sealcomprises an annular non-extrusion spring which is located proximate anintersection of the base portion and the beveled portion.
 7. The swiveljoint of claim 1, wherein the male nose portion further comprises aconical side wall which diverges radially outwardly from the cylindricalside wall in a direction toward the axially outer end of the recess, andwherein the second primary seal sealingly engages both the cylindricalside wall and the conical side wall.
 8. The swivel joint of claim 7,wherein the second primary seal comprises in cross section a radiallyinner peak and a beveled portion which diverges radially outwardly fromthe peak in a direction toward an axially outer end of the recess, andwherein the annular peak sealingly engages the cylindrical side wall andthe beveled portion sealingly engages the conical side wall.
 9. A swiveljoint comprising: a tubular female member which includes a female raceportion having an axially extending inner annular recess, a female innerend portion which is formed at an axially inner end of the recess, and anumber of inner annular grooves which are formed in the recess coaxiallytherewith; a tubular male member which includes a male race portionhaving an annular outer surface which is configured to be received inthe recess, a male nose portion which is formed at an end of the malerace portion, and a number of outer annular grooves which are formed onthe outer surface coaxially therewith; wherein the male race portion ispositioned in the female race portion such that the male nose portion islocated adjacent the female inner end portion and each outer groove isaligned with a corresponding inner groove to thereby define a number ofannular bearing races within which a plurality of balls are received tothereby rotatably connect the male member to the female member; a firstprimary seal which is positioned between the male nose portion and thefemale inner end portion; and a second primary seal which is positionedbetween the male nose portion and the female inner end portion radiallyoutwardly of the first primary seal; wherein the male and female membersdefine a flow bore through the swivel joint which is sealed by the firstprimary seal and, in the event of a failure of the first primary seal,the second primary seal; wherein the second primary seal is mounted inan annular seal pocket which is formed in the female inner end portion,said seal pocket comprising a floor and first and second radiallyoutwardly extending side walls between which the second primary seal ispositioned; and wherein the second primary seal comprises a generallyrectangular cross section having a first axially outer sealing facewhich sealingly engages a radially extending first end wall on the malenose portion.
 10. The swivel joint of claim 9, wherein the first primaryseal is mounted in an annular seal pocket which is formed in the femaleinner end portion, and wherein the first primary seal comprises agenerally rectangular cross section having a second axially outersealing face which sealingly engages a radially extending second endwall that is formed on the male nose portion radially and axiallyinwardly of the first end wall.
 11. The swivel joint of claim 10,wherein the second end wall extends radially outwardly from the flowbore.
 12. The swivel joint of claim 11, wherein the second end wall isconnected to the first end wall by an axially extending cylindrical sidewall.
 13. A swivel joint comprising: a tubular female member whichincludes a female race portion having an axially extending inner annularrecess, a female inner end portion which is formed at an axially innerend of the recess, and a number of inner annular grooves which areformed in the recess coaxially therewith; a tubular male member whichincludes a male race portion having an annular outer surface which isconfigured to be received in the recess, a male nose portion which isformed at an end of the male race portion, and a number of outer annulargrooves which are formed on the outer surface coaxially therewith;wherein the male race portion is positioned in the female race portionsuch that the male nose portion is located adjacent the female inner endportion and each outer groove is aligned with a corresponding innergroove to thereby define a number of annular bearing races within whicha plurality of balls are received to thereby rotatably connect the malemember to the female member; a first primary seal which is positionedbetween the male nose portion and the female inner end portion; a secondprimary seal which is positioned between the male nose portion and thefemale inner end portion radially outwardly of the first primary seal;an annulus which is formed between the female inner end portion and themale nose portion and is connected to the flow bore; and a monitor portwhich extends from a radial outer surface of the female member to theannulus; wherein the male and female members define a flow bore throughthe swivel joint which is sealed by the first primary seal and, in theevent of a failure of the first primary seal, the second primary seal;wherein the annulus comprises a first portion which extends between thefirst and second primary seals; wherein the monitor port extends throughthe female member to the first portion of the annulus and is sealed by aremovable plug member; and wherein a failure of the first primary sealcan be detected by removing the plug member and determining whetherfluid from the flow bore has entered the monitor port.
 14. The swiveljoint of claim 13, wherein the annulus comprises a second portion whichextends between the second primary seal and an axially innermost bearingrace and the swivel joint further comprises: a leak detection port whichextends through the female member to the second portion of the annulus;wherein a failure of both the first and second primary seals can bedetected by observing whether fluid from the flow bore has escapedthrough the leak detection port.
 15. The swivel joint of claim 13,further comprising: a plug holder which is positioned in the monitorport radially outwardly of the plug member, the plug holder comprisingan axial through bore; wherein the plug member is configured such that,in the event of a failure of the first primary seal, pressure in thefirst portion of the annulus will force at least a portion of the plugmember through the axial through bore to thereby provide a visualindication that the first primary seal has failed.
 16. The swivel jointof claim 15, further comprising a retainer which is secured in themonitor port radially outwardly of the plug holder to thereby secure theplug holder in the monitor port.
 17. The swivel joint of claim 16,further comprising a keeper which is positioned in the monitor portbetween the plug holder and the retainer, the keeper comprising a cavityon its radially inner end which is aligned with the through bore andinto which the portion of the plug member will extrude in the event of afailure of the first primary seal.
 18. The swivel joint of claim 17,wherein an annular portion of the plug holder surrounding the throughbore is sealed to the monitor port and a radially inner end of thekeeper is sealed to a radially outer end of the plug holder over thethrough bore to thereby retain the pressure in the monitor port.